Explosion-proof micro-cell thermal conductivity detector

Abstract

The utility model belongs to the technical field of detectors in analysis instruments, and particularly discloses a flame-proof micro-cell thermal conductivity detector. The thermal conductivity detector is used for solving the problem that the detection sensitivity of a traditional thermal conductivity detector is affected due to large size of a thermal conductivity cell. Comprising a tick valve, a homocentric-square-like gas flow cell, a first carrier gas inlet pipe, a second carrier gas inlet pipe, a sample gas inlet pipe and an exhaust pipe. The gas flow cell comprises a micro thermal conductivity cell and a conventional cell which are oppositely arranged up and down, a heating wire is welded on the micro thermal conductivity cell, and the volume of the micro thermal conductivity cell is 4 microliters. A first carrier gas inlet, a first sample gas inlet and a second carrier gas inlet are formed in a gas flow passage on the right side of the gas flow cell, the first carrier gas inlet is positioned on one side of the micro thermal conductivity cell, the second carrier gas inlet is positioned on one side of the conventional cell, and the first sample gas inlet is positioned between the first carrier gas inlet and the second carrier gas inlet; and the tick valve controls carrier gas switching of the first carrier gas inlet pipe and the second carrier gas inlet pipe.

Description

Technical Field

[0001] The utility model belongs to the technical field of detectors in analytical instruments, and particularly relates to an explosion-proof micro-cell thermal conductivity detector. Background Art

[0002] The principle of thermal conductivity detector (TCD) is to detect the concentration change of gas components based on the difference in thermal conductivity. The thermal conductivity detector uses the difference in thermal conductivity between the detected component and the carrier gas to detect the concentration change of the component. In the thermal conductivity detector, there is usually a thermal conductivity cell, which is equipped with a thermistor (such as tungsten wire or rhenium tungsten wire), whose resistance increases with the increase of temperature. When a constant direct current passes through the thermal conductivity cell, the hot wire is heated. When the carrier gas passes through the thermal conductivity cell, due to the heat conduction effect, part of the heat of the hot wire is taken away by the carrier gas, and part is transferred to the cell body. When the heat generated by the hot wire reaches a balance with the heat dissipated, the temperature of the hot wire stabilizes at a certain value, and the resistance of the hot wire is also stabilized at a certain value. The reference cell and the measuring cell are both filled with pure carrier gas. Since the same carrier gas has the same thermal conductivity, the resistance values ​​of the two arms are the same, the bridge is balanced, and there is no signal output. When the sample enters the detector, the pure carrier gas flows through the reference cell, and the carrier gas carrying the component gas flows through the measuring cell. Since the thermal conductivity of the binary mixed gas of the carrier gas and the component to be measured is different from that of the pure carrier gas, the heat dissipation in the measuring cell changes, causing a difference in the resistance value of the hot wire in the reference cell and the measuring cell hole, the bridge loses balance, and the detector outputs a voltage signal. This voltage signal is proportional to the concentration of the component, so the concentration of the component can be determined by measuring the size of the voltage signal.

[0003] In addition, with the continuous advancement of industrial technology, the requirements for safety monitoring and environmental protection are becoming increasingly higher. Although traditional thermal conductivity detectors can meet the needs to a certain extent, they also have the following problems: (1) The thermal conductivity cell of traditional thermal conductivity detectors is large in size, which causes the gas sample to diffuse into the thermal conductivity cell and cannot completely pass through the hot wire, thus affecting the detection sensitivity. (2) The switching frequency of the tick valve component equipped with the traditional single-wire thermal conductivity detector has certain limitations, which affects the detection sensitivity. (3) The traditional thermal conductivity detector is a non-explosion-proof structure and cannot be used directly in flammable and explosive occasions. It has a complex structure and a large size, which brings great inconvenience to its use. (4) The thermistor used in the traditional thermal conductivity detector is a rhenium tungsten wire, which is easily corroded by components such as hydrogen sulfide and hydrogen chloride, and is easily oxidized at high temperatures, resulting in changes in resistance or hot wire breakage. Utility Model Content

[0004] The utility model aims to provide a flameproof micro-cell thermal conductivity detector, which effectively solves the problem that the detection sensitivity of the traditional thermal conductivity detector is affected by the large volume of the thermal conductivity cell.

[0005] To solve the above technical problems, the technical solution adopted by the present utility model is as follows:

[0006] An explosion-proof microcell thermal conductivity detector, comprising a tick valve, a gas flow cell in the shape of a "return" character, a first carrier gas inlet pipe, a second carrier gas inlet pipe, a sample gas inlet pipe and an exhaust pipe. The gas flow cell includes a micro thermal conductivity cell and a conventional cell arranged oppositely up and down. The micro thermal conductivity cell and the conventional cell are connected. A hot wire is welded on the micro thermal conductivity cell, and the volume of the micro thermal conductivity cell is 4 μL.

[0007] A first exhaust port is provided on the gas flow path on the left side of the gas flow cell, and the first exhaust port is connected to the exhaust pipe.

[0008] A first carrier gas inlet, a first sample gas inlet and a second carrier gas inlet are provided on the gas flow path on the right side of the gas flow cell. The first carrier gas inlet is on one side of the micro thermal conductivity cell, the second carrier gas inlet is on one side of the conventional cell, and the first sample gas inlet is between the first carrier gas inlet and the second carrier gas inlet. The first interface of the tick valve is connected to the first carrier gas inlet through the first carrier gas inlet pipe, the second interface of the tick valve is connected to the second carrier gas inlet through the second carrier gas inlet pipe, the sample gas interface of the tick valve is connected to the first sample gas inlet through the sample gas inlet pipe, and the tick valve controls the carrier gas switching of the first carrier gas inlet pipe and the second carrier gas inlet pipe.

[0009] Furthermore, it further includes an explosion-proof upper cover, an explosion-proof lower housing and a cell upper cover. The cell upper cover is welded above the gas flow cell, and the explosion-proof upper cover is above the explosion-proof lower housing and the two are connected by screws.

[0010] Furthermore, a heating rod and a platinum thermal resistor are installed on the explosion-proof lower housing.

[0011] Furthermore, a layer of silicon oxide coating is coated on the outer surface of the hot wire.

[0012] Furthermore, the first carrier gas inlet pipe and the second carrier gas inlet pipe pass through the explosion-proof lower housing and are respectively connected to the first carrier gas inlet and the second carrier gas inlet.

[0013] Furthermore, a second sample gas inlet and a second exhaust port are provided at the bottom end of the explosion-proof lower housing. The sample gas inlet pipe is connected to the second sample gas inlet, the first sample gas inlet is connected to the second sample gas inlet through a pipeline, the exhaust pipe is connected to the second exhaust port, and the first exhaust port is connected to the second exhaust port through a pipeline.

[0014] Compared with the prior art, the beneficial technical effects of the present utility model are as follows:

[0015] (1) The micro-thermal conductivity cell of the present utility model has a volume of only 4 μL, effectively preventing gas samples from entering the thermal conductivity cell to form diffusion, thereby greatly enhancing the detection sensitivity.

[0016] (2) The present utility model adopts a tick valve with a high switching frequency, which has a short interval and good stability, ensuring good performance of the detector.

[0017] (3) The present utility model welds a cell upper cover above the gas flow cell. The explosion-proof upper cover and the explosion-proof lower housing are tightly locked by screws, effectively solving the explosion-proof problem and ensuring the safety of the gas flow cell, so it is suitable for direct use in flammable and explosive occasions. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] Figure 1 is a perspective view of the three-dimensional structure of the present utility model.

[0019] Figure 2 is a top perspective view of the present utility model (the tick valve is not shown). DETAILED DESCRIPTION OF THE EMBODIMENTS

[0020] An explosion-proof micro-cell thermal conductivity detector, as Figure 1 and Figure 2 shown, includes an explosion-proof upper cover 1, an explosion-proof lower housing 2, a cell upper cover 3, a tick valve 4, a gas flow cell 5 in the shape of a "return" character, a first carrier gas inlet pipe 6, a second carrier gas inlet pipe 7, a sample gas inlet pipe 8, and an exhaust pipe 9. A heating rod 10 and a platinum thermal resistor 11 (PT100) are installed on the explosion-proof lower housing 2.

[0021] The explosion-proof upper cover 1 and the explosion-proof lower housing 2 adopt a full blind hole design. A cell upper cover 3 is welded above the gas flow cell 5. The explosion-proof upper cover 1 is located above the explosion-proof lower housing 2 and the two are tightly connected by screws, thus realizing the explosion-proof design and ensuring the safety of the gas flow cell, making this embodiment suitable for direct use in flammable and explosive occasions.

[0022] The gas flow cell 5 includes a micro-thermal conductivity cell 12 and a conventional cell 13 arranged opposite to each other up and down. The micro-thermal conductivity cell 12 and the conventional cell 13 are connected. A hot wire is welded on the micro-thermal conductivity cell 12, and a layer of silicon oxide coating is coated on the outer surface of the hot wire, greatly enhancing the corrosion resistance of the hot wire. The volume of the micro-thermal conductivity cell 12 is only 4 μL, effectively preventing gas samples from entering the micro-thermal conductivity cell 12 to form diffusion, thereby greatly enhancing the detection sensitivity.

[0023] As Figure 1 shown, a first exhaust port 14 is provided on the gas flow path on the left side of the gas flow cell 5, and a second exhaust port is provided at the bottom end of the explosion-proof lower housing 2. The exhaust pipe 9 is connected to the second exhaust port, and the first exhaust port 14 and the second exhaust port are connected by a pipe.

[0024] like Figure 1 and Figure 2 As shown, the gas flow passage on the right side of the gas flow cell 5 is provided with a first carrier gas inlet 16, a first sample gas inlet 17 and a second carrier gas inlet 18, the first carrier gas inlet 16 is located on one side of the micro-thermal conductivity cell 12, the second carrier gas inlet 18 is located on one side of the conventional cell 13, and the first sample gas inlet 17 is located between the first carrier gas inlet 16 and the second carrier gas inlet 18. A second sample gas inlet is provided at the bottom end of the explosion-proof lower housing 2, the sample gas inlet pipe 8 is connected to the second sample gas inlet, and the first sample gas inlet 17 is connected to the second sample gas inlet through a pipeline.

[0025] The sample gas interface of the tick valve 4 is connected to the first sample gas inlet 17 through the sample gas inlet pipe 8. The first interface of the tick valve 4 is connected to the first carrier gas inlet 16 through the first carrier gas inlet pipe 6, and the second interface of the tick valve 4 is connected to the second carrier gas inlet 18 through the second carrier gas inlet pipe 7. The first carrier gas inlet pipe 6 and the second carrier gas inlet pipe 7 are connected to the first carrier gas inlet 16 and the second carrier gas inlet 18 respectively after passing through the explosion-proof lower shell 2. The tick valve 4 controls the carrier gas switching of the first carrier gas inlet pipe 6 and the second carrier gas inlet pipe 7. In this embodiment, the switching frequency of the tick valve 4 is high, the interval is short, and the stability is good, which ensures the good performance of the explosion-proof micro-cell thermal conductivity detector.

[0026] The working principle of the utility model is as follows: when the first carrier gas inlet pipe 6 is opened, the carrier gas enters the gas circulation pool 5 and fills the micro thermal conductivity pool 12 and the conventional pool 13. At this time, the sample gas entering through the sample gas inlet pipe 8 will enter the conventional pool 13 under the compression of the carrier gas. At this time, the micro thermal conductivity pool 12 circulates the carrier gas.

[0027] The tick valve 4 is switched, and the second carrier gas inlet pipe 7 is opened while the first carrier gas inlet pipe 6 is closed, and the carrier gas enters the gas circulation pool 5 and fills the micro thermal conductivity pool 12 and the conventional pool 13. At this time, the sample gas entering through the sample gas inlet pipe 8 will enter the micro thermal conductivity pool 12 under the compression of the carrier gas, and the micro thermal conductivity pool 12 is circulating the sample gas. The heat of the hot wire with a certain heat changes after the sample gas passes through it, and the resistance value of the hot wire changes after the heat changes. The resistance value is calculated by the mainboard control element under the two conditions and converted to obtain the quantitative result of the sample gas.

[0028] Of course, the above description is not a limitation of the present invention, and the present invention is not limited to the above examples. Changes, modifications, additions or substitutions made by technicians in this technical field within the essential scope of the present invention should also fall within the protection scope of the present invention.

Claims

1. A flameproof micro-cell thermal conductivity detector, characterized in that: It includes a tick valve, a gas flow cell in a shape similar to the Chinese character "回" (hui), a first carrier gas inlet pipe, a second carrier gas inlet pipe, a sample gas inlet pipe and an exhaust pipe. The gas flow cell includes a micro-thermal conductivity cell and a conventional cell which are arranged opposite to each other vertically. The micro-thermal conductivity cell and the conventional cell are connected. A hot wire is welded on the micro-thermal conductivity cell. The volume of the micro-thermal conductivity cell is 4 μL. A first exhaust port is provided on the gas flow path on the left side of the gas flow cell. The first exhaust port is connected to the exhaust pipe. A first carrier gas inlet, a first sample gas inlet and a second carrier gas inlet are provided on the gas flow path on the right side of the gas flow cell. The first carrier gas inlet is on the side of the micro-thermal conductivity cell. The second carrier gas inlet is on the side of the conventional cell. The first sample gas inlet is between the first carrier gas inlet and the second carrier gas inlet. The first interface of the tick valve is connected to the first carrier gas inlet through the first carrier gas inlet pipe. The second interface of the tick valve is connected to the second carrier gas inlet through the second carrier gas inlet pipe. The sample gas interface of the tick valve is connected to the first sample gas inlet through the sample gas inlet pipe. The tick valve controls the switching of the carrier gas in the first carrier gas inlet pipe and the second carrier gas inlet pipe.

2. The flameproof micro-cell thermal conductivity detector according to claim 1, characterized in that: It also includes an explosion-proof upper cover, an explosion-proof lower housing and a cell upper cover. The cell upper cover is welded above the gas flow cell. The explosion-proof upper cover is above the explosion-proof lower housing and the two are connected by screws.

3. The flameproof micro-cell thermal conductivity detector according to claim 2, characterized in that: A heating rod and a platinum thermal resistor are installed on the explosion-proof lower housing.

4. The flameproof micro-cell thermal conductivity detector according to claim 3, characterized in that: A layer of silicon oxide coating is coated on the outer surface of the hot wire.

5. The flameproof micro-cell thermal conductivity detector according to claim 4, characterized in that: The first carrier gas inlet pipe and the second carrier gas inlet pipe pass through the explosion-proof lower housing and are respectively connected to the first carrier gas inlet and the second carrier gas inlet.

6. The flameproof micro-cell thermal conductivity detector according to claim 5, characterized in that: A second sample gas inlet and a second exhaust port are provided at the bottom end of the explosion-proof lower housing. The sample gas inlet pipe is connected to the second sample gas inlet. The first sample gas inlet and the second sample gas inlet are connected by a pipe. The exhaust pipe is connected to the second exhaust port. The first exhaust port and the second exhaust port are connected by a pipe.

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